1. Field of the Invention
The present invention generally relates to display adjustment and balance methods for liquid crystal displays, LCDs. More particularly, a wide-range display position adjustment method is described. More particularly, this adjustment method allows the valid image to be moved to any position in the vertical or horizontal direction on the LCD panel and can even be rolled around.
2. Description of the Prior Art
FIG. 1 shows a basic display description of the prior art. A display 110 is shown. Its resolution is 800 by 600 or 800 pixels horizontally by 600 lines vertically. Also shown is a basic display timing diagram. The Hsync signal 120, which is active when the signal goes to zero, is shown. Also shown is the data enable, DE, signal 130, which is active when DE goes high. The two dotted lines at 140 and 150 show where DE rises and falls respectively. The dotted lines are extrapolated to the Hsync waveform to show the DE transitions in relation to the active Hsync times. The DE 130 signal denotes when the display data is enabled and active on the display screen.
FIG. 2 shows the vertical display control signals in more detail. The main vertical sync signal Vsync 210 is shown. It is active when the signal is at the low level 265. The Vsync signal is used to synchronize the ends of one screen refresh and the start of the next screen refresh. FIG. 2 shows the rising edge of Vsync at 260 and the falling edge of Vsync at 295. The Vtotal parameter is shown 250. It denotes the number of displayable lines on the display. These lines are distributed vertically. FIG. 2 also shows the Hsync signal 220. During the Vtotal time period, the number of Hsync pulses equals the number of horizontal lines, plus the number of Hsync pulses that occur during the Vsync time. FIG. 2 shows these video signals red, green, blue, R, G, B 230. The Vsize parameter 290 indicates how many displayable scan lines appear on the display. Also shown in FIG. 2 is the vertical front porch parameter, Vfp 280. The vertical front porch is that portion of time between the end of the displayable lines and the beginning of the active Vsync, which is when Vsync falls. The end of the displayable lines is denoted by the fall 285 of the Line Enable LE signal 240. There are no displayable lines during the Vfp. The vertical back porch, Vbp 270 is the time period between the rise of the Vsync 260 signal and the rise 275 of the LE signal 240. There are no displayed lines during the Vbp.
FIG. 3 shows the horizontal display control signals in more detail. The horizontal sync signal is Hsync 310 is shown. It is active when the signal is a low level 345. The Hsync signal is used to synchronize the end of one display line and the start of the next display line. FIG. 3 shows the rising edge of Hsync at 340 and the falling edge of Hsync 355. FIG. 3 also shows the three video signals red, green, and blue, RGB, 320. Also shown in FIG. 3 is the Data Enable signal, DE 330. When DE 330 is high & active, pixels are being updated and displayed on the display. FIG. 3 shows the horizontal backporch, Hbp 350. This is the time period between the rise 340 of Hsync 310 and the rise 335 of the DE 330 signal. There is no updating of pixels on the screen during this time period. Also shown is the horizontal frontporch Hfp 360. This is the time period between the fall of DE 330 and the fall of Hsync 355. There is no updating of pixels on the screen during this time period. The Hsize or horizontal size parameter 370 indicates how many displayable pixels appear on the display horizontally.
U.S. Pat. No. 6,304,253 (Sung, et al.) “Horizontal Position Control Circuit for High Resolution LCD Monitors” describes a horizontal position control circuit for liquid crystal displays.
U.S. Pat. No. 5,975,705 (Lee) “LCD Position Determination Apparatus for LCD Projector” describes a position determination apparatus for a liquid crystal display projector.